The following relates generally to memory devices and more specifically to maintaining the performance of ferroelectric memory cells that store logic values for extended periods of time.
Memory devices are widely used to store information in various electronic devices such as computers, wireless communication devices, cameras, digital displays, and the like. Information is stored by programing different states of a memory device. For example, binary devices have two states, often denoted by a logic “1” or a logic “0.” In other systems, more than two states may be stored. To access the stored information, the electronic device may read, or sense, the stored state in the memory device. To store information, the electronic device may write, or program, the state in the memory device.
Various types of memory devices exist, including random access memory (RAM), read only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, and others. Memory devices may be volatile or non-volatile. Non-volatile memory (e.g., flash memory) can store data for extended periods of time even in the absence of an external power source. Volatile memory devices (e.g., DRAM) may lose their stored state over time unless they are periodically refreshed by an external power source. A binary memory device may, for example, include a charged or discharged capacitor. A charged capacitor may, however, become discharged over time through leakage currents, resulting in the loss of the stored information. Certain features of volatile memory may offer performance advantages, such as faster read or write speeds, while features of non-volatile memory, such as the ability to store data without periodic refreshing, may be advantageous.
FeRAM may use similar device architectures as volatile memory but may have non-volatile properties due to the use of a ferroelectric capacitor as a storage device. FeRAM devices may thus have improved performance compared to other non-volatile and volatile memory devices. A ferroelectric memory cell of the FeRAM device may store a logic state (e.g., logic 1) for an extended period of time (e.g., hours, days, months, etc.). Over this period of time, ferroelectric domains within a ferroelectric capacitor of the ferroelectric memory cell may shift, the magnitude and effects of which may increase with time. As a result of this shifting, the ferroelectric memory cell may experience degraded performance during subsequent write or read operations.